This invention relates to a stationary magnetic frequency multiplier that comprises laminated iron members, a polyphase primary winding and a secondary winding. The iron members form a closed magnetic circuit and at least one of the members has slots, the primary winding is arranged to have a number of pole pairs p.sub.1, and the secondary winding is magnetically coupled to the primary winding and has a number of pole pairs p.sub.2 equal to an odd multiple of the number of pole pairs p.sub.1 of the primary winding. In this multiplier a cross section of the iron members is saturated by the magnetic field produced by the primary winding, if it is supplied with a certain primary voltage at a certain frequency, and the primary and secondary windings are arranged so that a voltage can be induced at the terminal of the primary winding only by the fundamental of a field with a number of pole pairs p.sub.1 and no voltage can be induced by the same fundamental at the terminals of the secondary winding. The primary and secondary windings are formed as ring windings and are arranged in two rows of slots in such a manner that they set up travelling fields if fed in the polyphase mode. A magnetic return is provided by laminated iron members adjacent the ends of the teeth of the slotted iron member.
Such a travelling-field design of the frequency multiplier is proposed in U.S. application Ser. No. 127,575, in which the slotted zone of the iron member in question extends over an even multiple of the pole pitch of the primary winding since only then is the algebraic sum of all tooth fluxes permanently equal to zero and, therefore, no further flux path is required, besides the teeth, between the iron members provided with the windings and the iron members forming the magnetic return.
In order to obtain freedom from harmonics of the primary and secondary winding, it is preferable that the number of slots per pole and leg not be too small. The more slots are required, the higher the secondary frequency and, as a result, the higher the number of poles of the secondary winding. For technological reasons, there is a limit to how small the teeth and the slots that define them can be made. The number of slots required for two full primary pole pitches can, therefore, require the slotted zone of the iron member to be so long that the dimensions and proportions of the iron member become difficult to deal with, especially in the case of frequency multipliers with lower power ratings.